Cathode for thermionic tubes



Feb. 7, E950 F. A. GOULDING CATHODE FOR THERMIONIC TUBES Filed March 24,1947 if 0 v NZ 2 w WA? Patented Feb. 7, 1950 CATHODE FOR THERMIONICTUBES Francis Adolphus Goulding, Harrow-on-the-Hill,

England, assignor to Hivac Limited, Harrowon-the-Hill, England, aBritish company Application March 24, 1947, Serial No. 736,731 In GreatBritain April 1, 1946 The present invention concerns improvements in orrelating to the manufacture of thermionic valves and more particularlyconcerns the mounting of a filament.

An object of the invention is to mount a filament in such a way that itforms a complete'unit in itself of plate-like form which is suitable forexample for inserting with a plate-like grid or grids and a plate-likeanode or anodes in a stack as described in Diggles Application Ser. No.735,445.

According to a feature of the invention the filament lies substantiallyin the plane of a mica plate or plates and extends across an opening insaid plate or plates.

According to another feature of the invention the filament is supportedbetween and across openings in two mica plates which are themselvessecured together with the filament between them.

A preferred form of carrying the invention into effect will be describedby way of example with reference to the accompanying drawing which is aperspective view of a filament mount ing, on an enlarged scale.

Two rectangular plates of mica I which are conveniently similar in allrespects are each provided with a long rectangular opening 2 at one sideand at the other side with two pairs of narrow, spaced slots 3'. Theplates I are placed over one another so that all the openings in oneplate align with all the openings in the other plate, and are heldtogether by two nickel strips 1 one of which passes through the twoslots 3 of a pair and the other passes through the two slots 3 of theother pair. The strips I are bent over to hold the plates togetherfirmly. To one strip 1 is secured a curved spring 6 and to the other anextension nickel strip 5. The filament 4 is provided with tags at eachend and these are welded or swaged respectively to the curved spring 6and the extension strip 5. It is arranged that the filament extendscentrally along the opening 2 and passes at each end between the twoplates I. The strips 1 are respectively swaged or welded to two filamentconnecting or terminal wires.

Such an arrangement enables the filament wire to be assembled, mounted,tensioned and tested prior to inclusion in a valve assembly. If thegrids are also of plate form having openings of equal size to thefilament plate-openings and are of such a reduced size that when placedagainst the filament they do not reach the nickel tags it will beappreciated that the stacking of the electrodes can take place asdescribed in the application above referred to.

11 Claims. (Cl. 250-275) It will be appreciated that the opening 2 mayalso be placed centrally of the plates I instead of along one edge.

It will further be appreciated that it is not essential to use twoplates I of mica but that one plate only may be used with suitableprecaution for subsequent insulation of the filament when the electrodestack is prepared.

I claim:

1. A planar filament mounting for thermionic tubes comprising a micaplate, a filament lying substantially in the plane of the mica plateextending across an opening in said plate and stretched between a metalextension strip supported on the mica plate and a spring supportedlaterally of the filament on the mica plate.

2. A filament mounting for thermionic tubes comprising two mica plateswhich are secured together with the filament between them and with thefilament supported between and across openings in said plates.

3. A planar filament mounting for thermionic tubes comprising a micaplate having an opening and slots therein, a filament lyingsubstantially in the plane of the mica plate and extending across theopening therein, metal strips passing through slots in the plates, ametal extension strip supported on the mica plate by one of said stripsand supporting one end of the filament, and a spring carried laterallyof the filament on the mica plate by means of one of said strips andserving as a support for the other end of the filament.

4. A planar filament mounting for thermionic tubes comprising a micaplate having an opening and slots therein, a filament lyingsubstantially in the plane of the mica plate and extending across theopening therein, metal strips passing through slots in the plates, ametal extension strip supported on the mica plate by one of said stripsand supporting one end of the filament, and a cantilever spring carriedlaterally of the filament on the mica plate by means of one of saidstrips and serving as a support for the other end of the filament.

5. A planar filament mounting for thermionic tubes comprising a micaplate having an opening and slots therein, a filament lyingsubstantially in the plane of the mica plate and extending across theopening therein, metal strips passing through slots in the plates, ametal extension strip supported on the mica plate by one of said stripsand supporting one end of the filament, and a cantilever spring carriedlaterally of the filament on the mica plate by means of. one

3 of said strips and serving as a support for the other end of thefilament, said opening in the mica plate being placed centrally thereof.

6. A planar filament mounting for thermionic tubes comprising a micaplate having an opening and slots therein, a filament lyingsubstantially in the plane of the mica plate and, extending across theopening therein, metal strips passing through slots in the plates, ametal extension strip supported on the mica plate by one of said stripsand supporting one end of the filament, and a cantilever spring carriedlaterally of the filament on the mica plate by means of one; of. saidstrips and servingas a support for the other end of the filament, saidopening in the mica plate lying at one edge of said plate.

7. A planar filament mounting for thermionic tubes comprising two thinmica plates secured together, said plates having registering openingsand slots therein, a filament lying between said plates, and extendingacross said opening, metal strips passing through slots in the plates, ametal extension strip supported on the mica, plate by one of said stripsand supporting one end. of the filament, and a spring carried laterallyoi the filament on the mica plate by means: of. one of said strips andserving as a support for the other end of the filament.

8. A planar filament mounting for thermionic tubes comprising a micaplate having an opening and a plurality of slots therein, a first metalstrip supported on said plate by passage through certain of said slots,a metal extension strip-carried' by said" first metal strip, a secondmetal strip supported on said plate bypassage. through other of saidslots, a spring carried by said second strip, a filament lyingsubstantially in the. plane of said mica plate and extending across the.opening therein and stretched between said metal extension strip andsaid spring.

9. A planar mounting for the filamentary oath.- ode of a thermionicvacuum tube comprising two mica plates held together in face-to-facerelationship and having aligned openings. therein, a filament wirelocated in between said plates and .4 spanning said aligned openings andtwo metal parts each of thin sheet form disposed substantially in theplane of said plates and held in position thereby and connectedrespectively to said filament wire beyond the opposing ends of saidaligned openings in said plates.

10. A. planar mounting for the filament of a thermionic vacuum tubecomprising two thin mica plates secured together in face-to-facerelationship and each having an opening therein, saidopenings being inalignment with one another, a first metal strip disposed substantiallyin the; plane of said plates and having a part held by'said plates and afurther part disposed beyond one end of said aligned openings, a secondmetal strip. disposed substantially in the plane of said plates andhaving a part held by said plates and a further part disposed beyond theopposite end of said aligned openings and a filament wire stretchedbetween said iurther parts of said first and second metal strips anddisposed, between saidplates and spanning said aligned openings.

11; A filament mounting for a thermionic vacuum tube comprising aU-shaped structure em.- bodying a mica-sheet member, a rigid first limbat metal. secured at one end to said mica-sheet member, a, resilientsecond limb of metal secured at one end' to said mica-sheet member and asingle. length of filamentv wire extending between the free ends of saidlimbs.

FRANCIS ADOLPHUS GOULDING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES. PATENTS Number Name Date Re. 15,278 Langmuir Jan. 31,1922 1,013,914 Whitney Jan. 9, 1912 1,608,535 Schwerin Nov; 30, 1926.

FOREIGN. PATENTS Number Country Date M 2358. Great Britain Nov. 16, 1939

